Many catheterization procedures are performed in conjunction with x-ray techniques in order to monitor the position of the catheter, to facilitate guiding of the catheter as it is navigated through the patient's vasculature to diagnose diseases of the cardiovascular and vascular system and to observe the procedure as it progresses. A wide variety of catheters are used by cardiologists and interventional radiologists in procedures that are observed fluoroscopically and recorded on x-ray film. Such catheters typically come in various sizes, commonly denominated as "French" sizes, so that the physician can select the correct size of catheter for the patient. One "French" size corresponds to a dimension of approximately 0.013 inches in diameter.
The selection of the correct size of catheter for the patient and the procedure at hand is important. For example, in a catheter intended to be engaged with the ostium of a coronary artery (such as an angiographic catheter or an angioplasty guiding catheter) the correct selection of catheter diameter affects the manner in which the tip of the catheter will seat in the coronary ostium.
In heart catheterization procedures it is a common preliminary practice to conduct an angiographic study of the coronary anatomy. Typically that involves placement of an angiographic catheter in the heart with the tip of the catheter in engagement with one of the two coronary ostia leading to the coronary arteries. Radiopaque liquid then is injected into the coronary arteries and an cineangiogram is made to record that image. The angiogram so made then can be studied by the cardiologist or surgeon in order to determine a suitable therapeutic approach. Often the therapeutic approach may involve a subsequent catheterization procedure such as, for example, angioplasty.
In a typical angioplasty procedure a specially formed guide catheter is navigated from an insertion site in the groin, through the patient's arteries so that its tip is in engagement with the selected coronary ostium. A balloon dilatation catheter then is selected, in an appropriate size as determined by the physician, and is advanced through the guide catheter and into the coronary arteries. The balloon catheter typically will be associated with a guidewire which may be separate from or integral with the balloon catheter and which aids in navigation of the catheter through the coronary arteries. The catheter is manipulated to locate the balloon within the obstructing stenosis. The balloon then is inflated under high pressure to forcefully dilate the artery and open the lumen to increase blood flow through the artery.
Typically, the initial angiographic procedure is performed some time in advance of the angioplasty procedure and often may be performed by a different physician. Also of interest in connection with the present invention is the fact that in many instances it is necessary to perform a follow-up angioplasty procedure, for example, when restenosis develops. Restenosis develops in a substantial number of angioplasty patients and, when it does occur, it can occur from between several days to several months or longer after the initial angioplasty.
In follow-up angioplasty procedures as well as in the initial procedures it would be of significant benefit to the patient and the physician if the physician knew exactly what catheters had been used in the previous procedure whether diagnostic or therapeutic. Although an entry sometimes may be made in the patient's medical records, often such notes may not be made or, if made, may not be in sufficient detail to include the precise size of catheter that was used in the previous procedure. Although the physician will examine the patient's previous x-rays, if information concerning the details of the catheter that was used in the previous procedures is not readily available, such as in entries on the patient's record, the size of the catheter that was used cannot be determined accurately. The x-ray image is not sufficiently accurate to enable determination of the size of catheter used.
Knowledge by the physician as to the precise size of catheter used in the prior procedures would increase the probability of selection of the proper size catheter in the first instance. By selecting the proper size of catheter, the necessity for catheter exchanges may be avoided. Consequently, the total time of the procedure and extent of exposure of the patient to x-ray radiation may be maintained at a minimum.
It would be desirable, therefore, to provide a means by which a physician could determine readily from the patient's x-ray image, such as an angiogram, the size of catheter that was used in that x-ray procedure. It is among the general objects of the invention to provide such a system.